AaronMcD
Structural
- Aug 20, 2010
- 273
I'm coming across this same issue as in this thread. Shear capacity with the hole is greater than 2/3Vp.
I'm wondering why this triggers a web buckling check, even if there is zero shear at the hole.
I have a compact W8 and a 3 inch hole. It passes if the hole is square, but fails if the hole is circular.
Basically, the shear capacity of the reduced section is less than the plastic shear capacity of said section it the tee aspect ratio is longer. So a longer tee aspect ratio means it "passes" the web buckling check, singe shear capacity is low relative to gross section plastic shear capacity. But with a short tee (small hole or narrow hole), if "fails" the web buckling check.
In chapter 5, the length of the hole is reduced to 0.45*diameter for shear checks in the specification (Specification for Structural Steel Beams with Web Openings, ASCE 1997). So for instance a 1 inch hole would require separate web buckling checks (but the checks aren't required for holes < 0.3d). So it seems any circular holes are much more likely to require web buckling checks.
But I'm confused as to why a square 3x3 hole is just fine but a 3" circle requires more checks. For a compact W8 regardless of load. If the load is zero, still needs extra checks.
So I can make the contractor weld plates, or tell them to make a square hole, which seems silly since we always prefer circles. My gut says this hole is no problem especially if a bigger square is no problem. And in the middle of a simply supported beam, I feel there is next to no risk of tee compression alone, mostly in the flange, buckling the web.
I've put waaaay more time into this than is warranted for one hole, but I feel I come up with enough hole requests to research, read the specs, make a spreadsheet, etc. and make it a 2 minute check next time.
I'm wondering why this triggers a web buckling check, even if there is zero shear at the hole.
I have a compact W8 and a 3 inch hole. It passes if the hole is square, but fails if the hole is circular.
Basically, the shear capacity of the reduced section is less than the plastic shear capacity of said section it the tee aspect ratio is longer. So a longer tee aspect ratio means it "passes" the web buckling check, singe shear capacity is low relative to gross section plastic shear capacity. But with a short tee (small hole or narrow hole), if "fails" the web buckling check.
In chapter 5, the length of the hole is reduced to 0.45*diameter for shear checks in the specification (Specification for Structural Steel Beams with Web Openings, ASCE 1997). So for instance a 1 inch hole would require separate web buckling checks (but the checks aren't required for holes < 0.3d). So it seems any circular holes are much more likely to require web buckling checks.
But I'm confused as to why a square 3x3 hole is just fine but a 3" circle requires more checks. For a compact W8 regardless of load. If the load is zero, still needs extra checks.
So I can make the contractor weld plates, or tell them to make a square hole, which seems silly since we always prefer circles. My gut says this hole is no problem especially if a bigger square is no problem. And in the middle of a simply supported beam, I feel there is next to no risk of tee compression alone, mostly in the flange, buckling the web.
I've put waaaay more time into this than is warranted for one hole, but I feel I come up with enough hole requests to research, read the specs, make a spreadsheet, etc. and make it a 2 minute check next time.
